LinuxSA Mailing list archives

  From: branko@senet.com.au
  To  : linuxsa@linuxsa.org.au
  Date: Sat, 24 Apr 1999 21:03:52 +0930 (CST)

Re: AMD-K6-2/400 runs cold?

>I have just set up an AMD K6-2/400, and the board is jumpered for 400MHz,
>and the BIOS claims it is 400MHz as well.
>
>I touched the great big ball-bearing fan/heat-sink unit that I added, and,
>to my surprise, it was cold. You could almost chill a beer on it.
>
>The CPU core voltage is 2.2 V, but, even so, I would have expected the HS
>to heat up. It concerns me.
[snip]..

Richard,

The temperature of the heatsink is not a good indicator of the CPU
temperature - well not if the heatsink is doing its job.  The
heatsink creates a thermal gradient going from whatever temperature
the CPU is at to something just a little above air temperature.
When fan forced air flow is used, the difference between heatsink and
ambient temperature is difficult to feel. 

I've got a K6-350, the lid is off at the moment and my heatsink feels
no warmer than, say, the case.  The hardware of my PC provides a much
more accurate way to tell what goes on.  When I boot up and go into
the BIOS set up, one of the options gives a display of several running
parameters such as fan speed, core and IO voltages and temperatures.
When I plugged in the CPU, I remember seeing a small 2 pin component
sticking up from the board inside the square of the ZIF socket, it is
reasonable to assume that it is a temperature sensor of some sort
(perhaps a thermistor).  When the CPU is installed, the sensor would
be pressed against its bottom surface.

The BIOS in my machine tells me the following: CPU temp 32C, system 
temp 25C.  A thermometer elsewhere in my house indicates just a wee
bit over 20C.  I would even regard these figures with a bit of suspicion.
If the CPU temp does indeed come from the sensor that I noticed inside
the ZIF socket, then all that its telling me is that its 32C somewhere on
the thermal gradient between the CPU and the temp sensor.  The motherboard
uses this parameter to shut down the PC when the temperature reaches
60C.  If I overclocked my CPU I could use this to understand how
close the system was getting to thermal shutdown/meltdown.

As for chilling beer - its not possible for a heatsink to enjoy a
lower than ambient surface temperature without some sort of active 
assistance such as refrigeration or a Peltier cell.

Regards,
-- 
Branko Bratkovic
branko@senet.com.au

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